On harelip and cleft palate

by William Rose

The palate is a more or less horizontal partition dividing the month from the nasal cavity, and consists of a firm bony plate in front (the hard palate) with a freely moveable membrano-muscular velum behind (the soft palate), which under varying conditions of muscular action can either open or close the communication between the nose and pharynx.

The bony palate forms the vaulted roof of the mouth, the central and posterior parts of which are nearly horizontal; and on all sides, except at the back, it is bounded by the alveolar ridge. Into its formation several bones enter; in the adult skull one usually sees posteriorly a cruciform suture indicating the limits of the superior maxillæ and palate bones; but even in the adult, evidence is forthcoming in the existence of traces of sutures to indicate that the anterior part of the palate is formed independently of the part immediately behind it. Thus Mr. Carless tells me that a cursory examination by him of a few dozen adult skulls picked up at random in the Museum of the College of Surgeons revealed the fact that in quite one half of them traces of sutures could be seen extending outwards from the posterior part of the anterior palatine canal; and a similar examination by him of 40 skulls from the Museum of King’s College of many nations and various ages showed a similar result. In almost all there was distinct evidence of the suture in the median line; in 21, the maxillo-intermaxillary suture was indicated; whilst in 10 skulls, representing the period from infancy to young adult life, both the above were seen in all, and 7 showed traces in addition of a suture placed between them on either side, and which we shall describe hereafter as the endo-mesognathic. Kölliker[34] similarly records that out of 325 adult skulls examined, 96 of them showed definite traces of the maxillo-intermaxillary suture. Albrecht[35] declares that nine tenths of the skulls in the Königsberg and Kiel Museums from children under five years of age reveal the existence of five intermaxillary sutures, proving that there are four separate portions to the so-called intermaxilla. Each portion carries an incisor tooth, and the canine is developed immediately at the junction between the outer portion and the maxilla. Occasionally there are three incisors on each side, the jaw being then called hexaprodontous; the extra tooth is developed from the inner segment of the intermaxilla (or endognathion), the outer segment (or mesognathion) carrying as usual only the lateral incisor. The accompanying illustrations well indicate this arrangement of sutures and teeth ([Figs. 26 and 27]); the importance of these facts will be emphasized later. All traces of the facial aspect of these sutures disappear quite early in life.

Figs. 26 and 27.—Diagrams to represent the normal human upper jaw of a child, with four and six incisors respectively, and also indicating the five intermaxillary sutures. (After Albrecht.)

EG, MG, XG. Endo-, meso-, and exo-gnathion. e. Inter-endognathic suture. f. Endo-mesognathic suture. g. Exo-mesognathic suture. i₁. Central incisor. i₂. Lateral incisor. iₐ. Accessory incisor. c. Canine. m₁. First temporary molar. m₂. Second temporary molar.

The bony surface of the roof of the mouth is perforated by numerous small foramina for the transmission of the nutrient vessels to the body of the bone, pitted for the lodgment of mucous glands, and grooved longitudinally for the transit of vessels. At the postero-external corners the posterior and accessory palatine canals give entrance to the posterior palatine vessels, and nerves; and anteriorly in the median line is the anterior palatine canal transmitting the naso-palatine vessels and nerves.

The soft palate is a moveable curtain, consisting of a membranous expansion or aponeurosis attached to the posterior extremity of the hard palate by firm fibrous tissue. Incorporated with it are five pairs of muscles, controlling its movements; it is covered by a smooth thin mucous membrane, and terminates posteriorly in the uvula. The arrangement of these muscles is important, not only from their normal physiological functions, but also from their irregular action and effects in cases of cleft palate ([Fig. 28]). They may be arranged in groups: two, the levator and tensor palati, form a superior group; the azygos uvulæ is intermediate; and the palato-glossus and palato-pharyngeus form an inferior set. Arising from the extremity of the petrous bone, the levator passes downwards, and spreading out below unites with its fellow in the whole length of the median raphe. The tensor arises from the navicular fossa of the internal pterygoid plate, and after being reflected around the hamular process, its action there being assisted by the interposition of a bursa, is attached to the anterior portion of the aponeurosis and to the hinder part of the bony palate. The combined action of these muscles raises and makes tense the velum, and in addition influences the Eustachian tube; but the levator is by far the more important. The azygoi uvulæ muscles arising from the median raphe and spine of the hard palate descend to the tip of that process, and are thus able to regulate its length.

Fig. 28.—Muscles of palate dissected. The cut represents the posterior nares and upper surface of the soft palate.

a. The levator palati. b. The inner bundle of fibres of the palato-pharyngeus, forming the posterior pillar of the fauces, c. The palato-glossus. d. The tensor palati; the cartilaginous extremity of the Eustachian tube is seen in front of this latter. e. The posterior extremity of the inferior turbinated bone. f. The septum. g g. The uvula on each side stretched apart. (Fergusson.)